The present invention relates to a method and equipment for supervising the discharge of molten metal from a vessel, particularly as to the impending end of casting metal; the stream of molten metal may pour from a casting ladle, tundish or other casting vessels, through a protective tube, the vessel having a controlled discharge opening.
Casting of metal under utilization of a vessel with a bottom opening through which the metal pours freely permits experienced personnel to ascertain just from the color of the pouring stream when the end of the casting is about to approach; the bottom opening has to be closed as soon as slag intermingles with the poured metal. Of course, such slag should be prevented from participating in the casting.
In accordance with recent developments in casting an effort has been made to better protect the stream of pouring metal against reoxidation in air and a cover tube has been used which extends between the molten metal in the mold or the tundish and the discharge opening of the ladle. Accordingly, it is no longer possible to just observe the color of the stream of molten metal. However, the problem of avoiding the flow of slag into the tundish or mold remains just the same. This is particularly true for example whenever several ladies are emptied into a tundish for continuous casting in one or several molds; the fire proof material in the tundish is particularly prone to be attacked by slag. Therefore, entry of slag in the tundish has to be avoided even though direct observation of the stream is not possible.
One can, of course, indirectly ascertain when the ladle is about to empty by tracking its weight but that kind of indication is not a particularly accurate one. Therefore, it was found necessary in such case to prematurely shut off the ladle to make sure that slag will not pour into the tundish or into the mold. In other words, one had to operate with a relatively high margin of safety amounting to a waste of considerable quantities of molten metal that remains in the ladle and is still usable but is in fact now discharged with the slag as waste.